Chromogenic dicyanomethylenepyrazolinones

ABSTRACT

Chromogenic dicyanomethylenepyrazolinone for thermographic recording processes and the corresponding cyanomethylene dyes of the formula ##STR1## in which R is hydrogen, hydroxyl, amino, alkyl, cycloalkyl, aryl, aralkyl or a heterocylic radical, T 1  and T 2 , independently of one another, are each hydrogen, unsubstituted or halogen-, hydroxyl-, cyano- or lower alkoxy-substituted alkyl having a maximum of 12 carbon atoms, cycloalkyl having 5 to 10 carbon atoms or unsubstituted or halogen-, cyano-, lower alkyl- or lower alkoxy-(ring)substituted phenalkyl or phenyl, or T 1  and T 2  together with the nitrogen linking them are a five- or six-membered heterocyclic radical, and rings A and B, independently of one another, are unsubstituted or substituted by halogen, cyano, nitro, lower alkyl, lower alkoxy, (lower alkyl)carbonyl or (lower alkoxy)carbonyl.

This is a divisional of application Ser. No. 363,650 filed on Jun. 8,1989, now U.S. Pat. No. 4,916,234.

The present invention relates to chromogenicdicyanomethylene-pyrazolinones and the corresponding cyanomethylene dyesand processes for their preparation and their use.

The chromogenic dicyanomethylenepyrazolinones according to the inventionhave the general formula ##STR2## in which R is hydrogen, hydroxyl,amino, alkyl, cycloalkyl, aryl, aralkyl or a heterocylic radical, T₁ andT₂, independently of one another, are each hydrogen, unsubstituted orhalogen-, hydroxyl-, cyano- or lower alkoxy-substituted alkyl having amaximum of 12 carbon atoms, cycloalkyl having 5 to 10 carbon atoms orunsubstituted or halogen-, cyano-, lower alkyl- or lower alkoxy-(ring)substituted phenalkyl or phenyl, or T₁ and T₂ together with the nitrogenlinking them are a five- or six-membered, preferably saturated,heterocyclic radical, and rings A and B, independently of one another,are unsubstituted or substituted by halogen, cyano, nitro, lower alkyl,lower alkoxy, (lower alkyl)carbonyl or (lower alkoxy)carbonyl.

In the definition of the radicals of the pyrazolinones, lower alkyl andlower alkoxy are those groups or parts of groups which have 1 to 5, inparticular 1 to 3, carbon atoms, for example methyl, ethyl, n-propyl,isopropyl, n-butyl, sec.-butyl, tert.-butyl or amyl or methoxy, ethoxy,isopropoxy, tert.-butoxy or tert. amyloxy.

For example, halogen is fluorine, bromine or, preferably, chlorine.Alkyl groups R, T₁ and T₂ can have 1 to 12 C atoms and be straight-chainor branched. Examples of these alkyl radicals are methyl, ethyl,n-propyl, isopropyl, n-butyl, sec.-butyl, amyl, n-hexane, 2-ethylhexyl,n-heptyl, n-octyl, isooctyl, n-nonyl, isononyl or n-dodecyl.

Substituted alkyl radicals in T₁ and T₂ can be in particular cyanoalkyl,halogenoalkyl, hydroxyalkyl or alkoxyalkyl each having preferably atotal of 2 to 6 carbon atoms, for example β-cyanoethyl, β-chloroethyl,γ-chloropropyl, β-hydroxyethyl, γ-hydroxypropyl, β-methoxyethyl orβ-ethoxyethyl.

Examples of T₁ and T₂ as cycloalkyl are cyclopentyl or preferablycyclohexyl.

R, T₁ and T₂ as aralkyl are usually phenylethyl, phenylisopropyl or inparticular benzyl, while R, T₁ and T₂ as aryl are advantageouslynaphthyl, diphenyl and in particular phenyl. The benzyl and phenylradicals can be substituted by halogen, trifluoromethyl, cyano, nitro,lower alkyl, lower alkoxy, (lower alkoxy)carbonyl or (loweralkyl)carbonyl.

Preferred substituents in the benzyl and phenyl group of the R and Tradicals are, for example, halogen, cyano, methyl, methoxy orcarbomethoxy. Examples of this type of araliphatic or aromatic radicalsare methylbenzyl, 2,4- or 2,5-dimethylbenzyl, chlorobenzyl,dichlorobenzyl, cyanophenyl, tolyl, xylyl, chlorophenyl, methoxyphenylor carbomethyoxyphenyl.

A heterocyclic radical R is in particular a 5- or 6-membered, preferablyoxygen-, sulfur- or nitrogen-containing heterocycle of aromaticcharacter. Examples of these heterocycles are thienyl, furyl, furfuryl,pyrrolyl, pyrazolyl, imidazolyl or pyridyl radicals. The heteroaromaticradicals are advantageously bound to the pyrazolinone ring via a carbonatom of the hetero ring.

Where T₁ and T₂ together with the common nitrogen atom are aheterocyclic radical, this radical is, for example, pyrrolidino,piperidino, pipecolino, morpholino, thiomorpholino or piperazino, forexample methylpiperazino. Preferred saturated heterocyclic radicals for--NT₁ T₂ pyrrolidino, piperidino or morpholino.

The substituent R is preferably lower alkyl, for example methyl, ethyl,propyl, or also amino, hydroxyl or phenyl.

T₁ and T₂ can be identical to or different from one another. T₁ ispreferably C₁ -C₈ alkyl, cyclohexyl, phenyl, tolyl, benzyl or inparticular lower alkyl such as methyl, ethyl or butyl. T₂ is preferablyhydrogen, lower alkyl or benzyl and especially methyl, ethyl or butyl.

Benzene rings A and B are preferably unsubstituted. However, they canhave 1 to 4 (preferably 1 to 2) substituents. Preferred substituents arehalogen, nitro, lower alkyl (in particular methyl) or lower alkoxy, forexample methoxy.

Particularly important dicyanomethylenepyrazolinones have the formula##STR3## in which R₁ is amino, hydroxyl, lower alkyl, cyclohexyl orphenyl, and T₃ is lower alkyl, cyclohexyl, phenyl, tolyl or benzyl, andT₄ is hydrogen, lower alkyl or benzyl, and ring D is unsubstituted orsubstituted by halogen, nitro, lower alkyl or lower alkoxy.

Of the dicyanomethylenepyrazolinones of the formula (2), those in whichR₁ is amino or lower alkyl, T₃ is lower alkyl and T₄ is hydrogen orlower alkyl and benzene ring D is unsubstituted or substituted by methylor halogen are preferred.

The dicyanomethylenepyrazolinones of the formula (1) and (2) are4'-aminophenyl-4-(1-phenyl-2-pyrazolin-5-one)malodinitrile compounds.They are prepared by adding an aromatic amine of the formula ##STR4## inwhich B, T₁ and T₂ are as defined above onto adicyanomethylenepyrazolinone compound of the formula ##STR5## in which Aand R are as defined above.

The addition reaction is advantageously carried out in protic solventsat a temperature of 20° to 60° C., preferably 30° to 50° C. Suitablesolvents of this type are lower alkanols, for example methanol, ethanol,isopropanol or butanol, ketones, for example acetone, methyl isopropylketone or diethyl ketone and acetonitrile, propionitrile,dimethylformamide and especially glacial acetic acid.

Suitable aromatic amines are in particular N-monoalkyl- orN,N-dialkylanilines, for example N-methylaniline, N-ethylaniline,N-isopropylaniline, N,N-dimethylaniline, N,N-diethylaniline,N,N-dibutylaniline and also N,N-dibenzylaniline, N-phenylaniline andN-phenylpyrrolidines.

The dicyanomethylenepyrazolinone compounds of the formula (4) which canbe used as starting materials are in particular4-dicyanomethylene-3-methyl-1-phenyl-2-pyrazolin-5-one, m.p. 178° C.,4-dicyanomethylene-3-methyl-1-p-tolyl-2-pyrazolin-5-one, m.p. 145° C.,4-dicyanomethylene-3-propyl-1-phenyl-2-pyrazolin-5-one, m.p. 110°-112°C., 4-dicyanomethylene-1,3-diphenyl-2-pyrazolin-5-one, m.p. 162° C. and4-dicyanomethylene-3-amino-1-phenyl-2-pyrazolin-5-one, m.p. 220° C.(dec.).

The starting materials of the formula (4) are novel. In general it canbe said that it is possible to obtain them, for example, by reaction ofa pyrazolinone compound of the formula ##STR6## in which A and R are asdefined above with tetracyanoethylene, advantageously in the presence ofan inert organic solvent, for example acetonitrile, propionitrile orlower alkanols, particularly ethanol or isopropanol, and at atemperature of 20° to 50° C.

The compounds of the formulae (1) and (2) according to the invention canbe used as colour formers in a thermoreactive recording material.

The hue of the printed image obtained in the heat-sensitive recordingmaterial can be red, violet or reddish blue, depending on the definitionof A and R, and the colour images are sharp and clear.

The heat-sensitive recording materials are used, for example, forrecording information, for example in electronic calculators,teleprinters, telex machines or in recording machines and measuringinstruments, for example electrocardiographs. The image formation(marking) can also take place manually by means of a heated pen. Afurther means of producing markings by means of heat are laser beams.

The heat-sensitive recording systems contain at least one substrate, forexample paper, synthetic paper or a plastic sheet and on top of it oneor more heat-sensitive layers containing thedicyanomethylenepyrazolinone compounds of the formulae (1) and (2).

Preferably, the thermoreactive recording material is prepared by usingmeltable, film-forming binders. These binders are usually water-soluble,while the dicyanomethylene-pyrazolinone compounds of the formulae (1)and (2) are insoluble in water. The binder should be capable ofdispersing and fixing the dicyanomethylenepyrazolinone compound at roomtemperature.

Upon exposure to heat, a proton and a cyanide ion are removed from thedicyanomethylene compound which acts as colour former and a colour isformed.

Water-soluble or at least water-swellable binders are, for example,hydrophilic polymers such as polyvinyl alcohol, polyacrylic acid,hydroxyethylcellulose, methylcellulose, carboxymethylcellulose,polyacrylamide, polyvinylpyrrolidone, carboxylated butadiene/styrenecopolymers, gelatin, starch or etherified corn starch.

The thermoreactive layers can contain further additives. To improve thewhiteness, to facilitate the printing of the papers and to prevent theheated pen from being glued on, these layers can contain, for example,talcum, titanium dioxide, zinc oxide, alumina, aluminium hydroxide,calcium carbonate (e.g. chalk), clays or also organic pigments, forexample urea/formaldehyde polymers. To make sure that the colour is onlyformed within a limited temperature range, substances such as urea,thiourea, diphenylthiourea, acetamide, acetanilide, benzenesulfanilide,stearamide, phthalic anhydride, metal stearates, for example zincstearate, phthalonitrile, dimethyl terephthalate or other suitablemeltable products which induce CN elimination can be added. Preferably,the thermographic recording materials contain waxes, for examplecarnauba wax, montan wax, paraffin wax, polyethylene wax, condensationproducts of higher fatty acid amides and formaldehydes and condensationproducts of higher fatty acids and ethylenediamine. If desired, therecording materials can also contain alkylene substances, for examplehydroxides or carbonates of alkali metals or, preferably open-chain orcyclic organic bases such as amines, alkanolamines, guanidines,pyridines or imidazole derivatives.

Upon exposure to heat, HCN is eliminated from thedicyanomethylenepyrazolinones of the formula (1) to givemonocyanomethylenepyrazolinones of the formula ##STR7## in which A, B,R, T₁ and T₂ are as defined above.

The compounds of the formula (6) are coloured products and can havevarious uses as dyes.

The preparative thermolysis is advantageously carried out by heating totemperatures of more than 70° C., preferably to temperatures of 80° to120° C. It is advantageously carried out in the presence of an inertorganic solvent, for example glacial acetic acid or dimethylformamide,and under reflux. If desired, it is also possible to add an alkali metalcompound, for example alkali metal carbonates or alkali metalbicarbonates, ammonium carbonate or ammonium bicarbonate.

The elimination of cyanide for preparing the dyes of the formula (6) canalso be carried out by photolysis, advantageously by irradiation, forexample with ultraviolet light and, especially, by means of a mercurylow-pressure lamp, in methanolic solution. In this case, it is notnecessary to isolate the dicyanomethylenepyrazolinones of the formula(1) during their preparation.

In the examples which follow, the percentages and parts given are byweight.

EXAMPLE 1

(a) 1.28 g of tetracyanoethylene are dissolved in 20 ml of acetonitrile,warmed to 40° C., and 0.87 g of 3-methyl-1-phenyl-2-pyrazolin-5-one isslowly added with stirring. The mixture is cooled, filtered off, andwater is added to the filtrate. The resulting precipitate is filteredoff and recrystallized from ethanol. This gives 1 g of the compound ofthe formula ##STR8## m.p. 178° C.

(b) 8.5 mmol of 4-dicyanomethylene-3-methyl-1-phenyl-2-pyrazolin-5-oneof the formula (i) are stirred together with 16.0 mmol ofN,N-dimethylaniline in 30 ml of glacial acetic acid at room temperature,which rapidly leads to the formation of a precipitate. Stirring at30°-50° C. is continued for another 2 hours, the precipitate is filteredoff and washed with ethanol. The compound is analytically pure. Thisgives a colourless compound of the formula ##STR9## Yield 86% of theory.m.p. 160° C.

A solution of this compound in methanol has a λ_(max) at 276 nm.

EXAMPLE 2

(a) 1.75 g of 3-amino-1-phenyl-2-pyrazolin-5-one are stirred with 1.28 gof tetracyanoethylene in 60 ml of ethanol at room temperature for 30minutes. 2.2 g of the resulting precipitate are then recrystallized frombutanol. This gives a compound of the formula ##STR10## m.p. 220° C.(dec.)

(b) 8.5 mmol of 3-amino-4-dicyanomethylene-1-phenyl-2-pyrazolin-5-one ofthe formula (ii) are stirred together with 16.0 mmol ofN,N-dimethylaniline in 30 ml of glacial acetic acid at room temperature,which rapidly leads to decolourization and formation of a precipitate.Stirring at 30°-50° C. is continued for another 2 hours, the precipitateis filtered off and washed with ethyl acetate. The compound isanalytically pure. This gives a colourless compound of the formula##STR11## Yield 80% of theory. m.p. 162° C.

A solution of this compound in methanol has a λ_(max) at 275 nm.

The procedure described in Examples 1 and 2 is repeated, using thecorresponding reactants, to give the dicyanomethylenepyrazolinoneslisted in Table 1 below. ##STR12##

                  TABLE 1                                                         ______________________________________                                                                             λ.sub.max (nm) in                 Ex.  R      --NT.sub.1 T.sub.2                                                                      m.p./°C.                                                                      Yield in %                                                                            methanol                                 ______________________________________                                        3    CH.sub.3                                                                             --N(C.sub.2 H.sub.5).sub.2                                                              180    99      262                                      4    CH.sub.3                                                                             --NHC.sub.2 H.sub.5                                                                     178    89      270                                      5    NH.sub.2                                                                             --N(C.sub.2 H.sub.5).sub.2                                                              188    92      270                                      6    NH.sub.2                                                                             --NHC.sub.2 H.sub.5                                                                     170    86      270                                      ______________________________________                                    

EXAMPLE 7

3 mmol of the compound of the formula (11) according to Example 1(b) areheated to reflux in 10 ml of dimethylformamide for 30 to 90 minutes. Themixture is cooled and water is added with stirring, which precipitatesthe compound of the formula ##STR13## in the form of green-blackcrystals. The compound is recrystallized from xylene or toluene. Meltingpoint 169° C. (dec.), yield 82% of theory.

A solution of this compound in methanol has a λ_(max) at 545 nm.

The procedure described in Example 7 is repeated, using the compoundsaccording to Examples 2 to 6, to give the cyanomethylenepyrazolinones ofthe formula (15) listed in Table 2. ##STR14##

                  TABLE 2                                                         ______________________________________                                                                              λ.sub.max (nm) in                Ex.  R      --NT.sub.1 T.sub.2                                                                       m.p./°C.                                                                      Yield in %                                                                            methanol                                ______________________________________                                         8   CH.sub.3                                                                             --N(C.sub.2 H.sub.5).sub.2                                                               133 dec.                                                                             90      560                                      9   CH.sub.3                                                                             --NHC.sub.2 H.sub.5                                                                      203 dec.                                                                             86      540                                     10   NH.sub.2                                                                             --N(CH.sub.3).sub.2                                                                      182 dec.                                                                             68      525                                     11   NH.sub.2                                                                             --N(C.sub.2 H.sub.5).sub.2                                                               188 dec.                                                                             70      535                                     12   NH.sub.2                                                                             --NH--C.sub.2 H.sub.5                                                                    222 dec.                                                                             78      525                                     ______________________________________                                    

EXAMPLE 13

A dispersion is prepared by grinding

2 g of the dicyanomethylenepyrazolinone compound according to Example 3,

7 g of a 10% aqueous solution of polyvinyl alcohol (Polyviol V03/1040)and

4 g of water

with glass beads, until a particle size of 2-4 μm is reached.

This dispersion is applied by means of a knife to a paper having aweight per unit area of 50 g/m². The amount of material applied is 4g/m² (dry weight). When developed by means of a precision hot press"System BASF", starting at 140°-150° C., a deep violet colour develops;contact time 80 seconds.

EXAMPLE 14

The procedure as described in Example 13 is repeated, except that thecompound described in Example 13 according to Example 3 is replaced by 2g of the dicyanomethylenepyrazolinone compound according to Example 6,to give, starting from 140°-150° C., a deep blackberry red dyeing.

What is claimed is:
 1. A chromogenic dicyanomethylenepyrazolinone of theformula ##STR15## in which R is a heterocylic radical, T₁ and T₂,independently of one another, are each hydrogen, unsubstituted orhalogen-, hydroxyl-, cyano- or lower alkoxy-substituted alkyl having amaximum of 12 carbon atoms, cycloalkyl having 5 to 10 carbon atoms orunsubstituted or halogen-, cyano-, lower alkyl- or loweralkoxy-(ring)substituted phenalkyl or phenyl, or T₁ and T₂ together withthe nitrogen linking them are a five- or six-membered heterocyclicradical, and rings A and B, independently of one another, areunsubstituted or substituted by halogen, cyano, nitro, lower alkyl,lower alkoxy, (lower alkyl)carbonyl or (lower alkoxy)carbonyl.
 2. Adicyanomethylenepyrazolinone according to claim 1, wherein R in formula(1) is a furyl, furfuryl, thienyl, pyrrolyl, pyrazolyl, imidazolyl orpyridyl radical.
 3. A dicyanomethylenepyrazolinone according to claim 1,wherein T₁ in formula (1) is C₁ -C₈ alkyl, cyclohexyl, phenyl, tolyl orbenzyl and T₂ is hydrogen, lower alkyl or benzyl.
 4. Adicyanomethylenepyrazolinone according to claim 1, wherein T₁ and T₂ informula (1) are each lower alkyl.
 5. A dicyanomethylenepyrazolinoneaccording to claim 1, wherein benzene rings A and B in formula (1) areunsubstituted or substituted by halogen, nitro, lower alkyl or loweralkoxy.